1. Technical Field
The technology of this disclosure pertains generally to a full duplex antenna arrays, and more particularly to a full-duplex antenna array utilizing indenting to improve transmit to receive isolation.
2. Background Discussion
Full-duplex radios are useful in numerous applications toward simplifying system hardware architectures and networking layer control protocols, while increasing spectral efficiencies since a full-duplex radio is able to “talk and listen” at the same time and same frequency. An additional benefit of a full-duplex radio is that fixed diplexer filters that are essential in conventional frequency duplex systems are no longer required in the full-duplex RF front-end. Consequently use of full duplex radios unleash further potential whereby radio operating frequency and bandwidth is selectable leading to a completely software reconfigurable radio system, for example cognitive radios for ultimately efficient usage of the spectrum.
In order for full-duplex radios to operate properly, the transmitter to receiver interferences must be sufficiently suppressed to prevent the transmitter signal and noise power leaked to the receiver from saturating the receiver and creating distortion. There are various conventional ways to reduce radio self-interference through antenna isolations. For space conscious applications, such as radios in mobile terminals, approaches to achieve the T/R isolation include the utilization of the pattern diversity, e.g., placing the receiving antenna at the nulls of the transmitting antenna array pattern, polarization diversity with an orthomode transducer (OMT) or circularly polarized antennas, and non-reciprocity with circulators. The spatial diversity approach cannot be applied to directional radios, where the pattern of the transmitting antenna is required to be identical to that of the receiving antenna. The polarization diversity approach also limits the choices of polarization in the transmission and reception of the waves. The non-reciprocity approach with circulators can only offer limited isolation and it is ineffective to the leakage from the antenna reflection of the transmitted power.
Accordingly, a need exists for full duplex radios with increased levels of transmitter-receiver isolation. The present disclosure fulfills that need and overcomes shortcomings of previous isolation techniques.